It is well-known that, with very few exceptions, rubber compositions are compounded with various other materials before being vulcanized (that is, cured) and made into an end product. It is well-known that fillers, such as carbon black and silica are included in vulcanized rubber to reinforce and strengthen it. Some of the compounding materials improve the properties of the end product in service. In some instances, these beneficial effects can be achieved by promoting interactions between the various chemicals, fillers and other materials, both organic and inorganic, present in the vulcanizates. For further discussions of rubber compounding and vulcanization see, for example, Encyclopedia of Polymer Science and Technology, published by John Wiley and Sons, New York (1970), particularly volume 12, page 280 and The Vanderbilt Rubber Handbook, R. T. Vanderbilt Company, Norwalk, Conn., 06855 (1968), particularly Sections 7, 8 and 9, beginning at page 407 and Section 11 at page 644.
Benzofurazan oxides, and their analogs and isomers are known, and many descriptions of procedures for their preparation have appeared in the art. See, for example, Kaufman, et al., "Chemical Reviews," volume 9, pages 429 and following (1959), and the description in Mallory, et al., "Organic Synthesis" collective volume IV, pages 74 and 75, John Wiley and Sons, New York (1963). The following U.S. Patents also describe procedures for preparing furazan oxides of various types: U.S. Pat. No. 4,185,018 to Fah; U.S. Pat. No. 3,528,098 to Shaw; and U.S. Pat. No. 2,424,199 to Ter Horst.
In considering previous descriptions of furazan oxides and related compounds, it should be noted that nomenclature used has not been consistant, in part due to uncertainty as to the structure of these compounds. In some instances, they are described as furazan oxide isomers, such as ortho dinitroso benzenes. They have also been described as di(nitrile oxides) and at various points referred as isobenzofuroxans, benzofuroxans, benzofurazan-N-oxides and benzofurazan oxides. It is believed that the latter is the modern and preferred nomenclature, and it shall be used in this specification and the appended claims.
The effects of furazan oxides and related compounds in rubber compositions have been reported. For example, Rehner and Flory reported in Industrial and Engineering Chemistry, volume 38, page 500 et seq. that ortho dinitroso benzene was inactive as a vulcanizing agent in butyl rubber. In contrast, the para isomer was reported to be very active as a vulcanizing agent. U.S. Pat. No. 3,931,121 to Davis, et al., describes the curing of elastomeric polymers with poly (chloronitroso) compounds. U.S. Pat. No. 3,931,106 to Crosby, et al., describes the use of dinitrile oxides which can be generated in situ from furoxans in the cross-linking of rubbers. In this regard, it should be noted that the aromatic furoxans of the present invention cannot isomerize to di(nitrile oxides) because the bond between the adjacent carbon atoms is part of an aromatic ring. U.S. Pat. No. 2,974,120 to Miller describes the use of nonaromatic furazan oxides as antioxidants and antidegradants in rubber. U.S. Pat. No. 2,905,582 to Coleman, et al., describes the use of nitroso compounds, including dinitroso compounds wherein the nitroso groups are on nonadjacent carbons in a method for bonding polyurethane resin to rubber bodies. Morita has described the use of N, 4-dinitroso-N-methyl aniline as an active chemical promoter for carbon black reinforcement of IIR, NR and SBR. The Rubber Chemistry and Technology, volume 49, page 119 and following (1976). Tanaka, et al., have reported studies of nitroso benzene in rubber in Kogyo Kagaku Zasshi 74(8) pages 1701-6 (1971).
PCT application No. PCT/US 83/00697 (now EPO application No. 83902018.7) published Nov. 24, 1983, describes the use of aromatic benzofurazan oxides in both filled vulcanizates and uncured rubber compositions. This application is owned by the owner of the present application. U.S. patent application Ser. No. 621,656, filed June 18, 1984, describes modified carbon black products comprising carbon black and aromatic furazan oxides. These products can be used in the present invention.